Anisotropic thermal conductivity of β-Ga_2O_3 at elevated temperatures: Effect of Sn and Fe dopants

摘要

The thermal conductivity of undoped, Sn-doped, and Fe-doped β-Ga_2O_3 bulk crystals was measured by the 3ω technique in the temperature range of 295-410 K. A unique approach for extracting the thermal conductivity along the lateral and transverse heat flow directions was used in order to determine the thermal conductivity along different crystallographic directions. The data analysis at room temperature confirmed the expected anisotropy of the thermal conductivity of β-Ga_2O_3, revealing the highest value of ~29 W/m K in the [010] direction. The thermal conductivity of the Sn-doped and Fe-doped β-Ga_2O_3 samples was found to be lower than that of the undoped samples due to the enhanced phonon-impurity scattering contribution, which reduces the thermal conductivity. This tendency was maintained for the thermal conductivity at elevated temperatures. The thermal conductivity in all samples decreased with increasing temperature, but the slope of the temperature dependence was found to depend on both the doping and the crystallographic orientation.